1. Field of the Invention
This invention relates to identification devices, security locks and keys, and access control systems. More particularly, it relates to an identification apparatus which measures hand dimensions and relations thereof for the purpose of identification.
2. Description of Prior Art
In the past, keys of both a mechanical and electrical nature have been used to restrict access to authorized individuals. The controlled access may be to physical areas, such as with the common lock and key, or to information, such as with computer terminal passwords, or to valuables, such as with automatic bank teller personal identification codes. The problem in these types of system is that access is provided to any keyholder, and the keys are transferable and easily lost, stolen or passed on.
More recently, identification devices relying upon biometric characteristics unique to an individual have been proposed. These devices measure and compare such things as voice, fingerprints, finger lengths, and signatures. They all suffer in performance because the characteristic of the person that is measured tends to vary greatly even for a given individual. For example, a person's fingerprints suffer day-to-day damage from scratches, abrasions and so on, that make accurate automatic identification very difficult. Also, they have proven to be very costly to manufacture because of such things as the precision required in the repeatable measurement of such fine detail as fingerprint minutia in fingerprint recognition systems, and high fidelity voice detection and background noise filtering in voice recognition systems.
It has been long known that people's hands differ in their size and shape, and that these differences can be used to distinguish one individual from another. Many goemetric characteristics of the hand can be measured and used to distinguish identity. For example, measurements such as length width, area, perimeter, thickness and so on, are unique to an individual. Also, combinations of these measurements, such as the ratio of length to width, can be used with good effect as identity discriminants.
Identification devices relying upon measurements of the large detail of the hand have been used with some success. However, these devices simply utilize the single dimensional measurement of finger lengths as an identity discriminating characteristic, and this does not present enough information for highly reliable identity determination.
Very recently, systems have been proposed which utilize two-dimensional pictures of the hand outline as acquired with an electronic digitizing camera. These systems have much better performance than those that rely simply upon finger length measurements. However, they are easily defeated by the use of an artifact in the shape of the hand of the claimed identity. Since only a simple two dimensional shadow image is required, such an artifact is easily constructed from a cardboard tracing of the hand of an authorized user. Such an outline can be obtained either surreptitiously, or through the cooperation of the authorized user.